Process for incorporating resins into paper



Nov. 5, 1963 R. c. MARTIN 3,109,769

PROCESS FOR INCORPORATING RESINS INTO PAPER Filed July 27. 1961 AQUEOUSSLURRY OF BEATEN CELLULOSE FIBER AQUEOUS DISPERSION OF A CHROMIUMCOORDINATION COMPLEX OF AN ACYCLIC ACIDO CARBOXYLIC ACID ADDED ANDDISPERSED INTO SLURRY TIMING- REACTION RESIN DISPERSION (AND ANY DESIREDFILLERS) ADDED AND DISPERSED INTO SLURRY TIMING- REACTION PAPER FORMEDAND DRIED INVENTOR. RAY C. MARTIN ATT'YS.

United States Patent 3,109,769 PROCESS FQR IYCORPORATING RESINS INTOPAPER Ray C. Martin, Freeport, Ill., assignor, by mesne assignments, toRay C. Martin, Freeport, Ill. Filed July 27, 1951, Ser. No. 127,147 17Claims. (Cl. 162-464) This invention relates to the art of paper making,and more particularly refers to a novel method of incorporating resinsand other additive materials into papermaking pulps at that point of thepaper making process generally termed as the wet end, and to the novelproducts produced thereby.

Unmodified paper and paper board made by conventional methods have manylimitations. The products are weak, permeable to water, oil and grease,and lack many of the properties generally desired in a finished paperproduct. To improve its properties, modifying or reinforcing materialssuch as resins, pigments, fillers and other related materials arecustomarily added to the paper.

The majority of processes currently used for incorporating thesematerials into paper may be characterized as secondary operations, thatis, they are methods for treating the paper after the paper itself hasbeen fabricated. Such secondary operations, or applications of themodifying materials made to the basic paper, usually from solvent orhot-melt systems, succeed at best only in applying a film of themodifying material on the paper surface, and to a degree filling theinterstices, but do not succeed in enabling the modifying material topenetrate and attach themselves to the fibers since the fibers andadditives are electrically repellent to each other. As a result, thefull benefit of the modifying materials is not realized. Moreover, theaddition of a separate treating step adds to the cost of processing.Even where wet-end processes have been used, complete retention of theadditive by the pulp generally has not been achieved, with the resultthat the excess additive is generally removed in the form of unattachedparticles, which, together with the fines from the process, frequentlycloud the water and render it nonreusable.

It is an object of the present invention to provide a process for theincorporation of resins and other modifying materials in an aqueousmedium into papenmaking pulp in the wet-end stage of the paper makingprocess.

It is a further object to provide such a process wherein the resins andother additives are removed from the aqueous medium in which they areapplied, and are tenaciously deposited upon the individual pulp fibers.

It is still further an object to provide such a process wherein thecoupling agent may he applied without the need for the subsequentaddition of insolubilizers.

It is still further an object to provide such a process wherein improvedand reinforced papers are produced in which the modifying substance isuniformly dispersed throughout the paper.

It is a further object to provide improved and reinforced paper productswhich, While incorporating the same modifying materials or additivecontent, exhibit greatly enhanced properties over products made by othermethods.

It is a further object to provide various useful improved 3,169,769Patented Nov. 5, 1963 and reinforced paper products by the methods ofthe present invention.

Other objects and advantages of the invention will become apparent fromthe description which follows, and from the appended claims.

The drawing comprises a flow sheet illustrating the essential process ofthe invention.

According to the invention, a water-soluble Werner type chromiumcoordination complex of an acylic acido carboxylic acid in aqueoussolution is added and thoroughly mixed into a circulating aqueoussuspension of paper-making pulp which has been first beaten in the usualmanner. The complex is absorbed by the pulp fibers and functions as acoupling agent for the subsequent attachment of modifying resins andother addit-aments. The modifying materials are preferably of suchnature that they may be provided in the form of an aqueous dispersioneither as a suspension, colloidal solution, or true solution. Othermaterials such as inorganic fillers may also be so added. When they areadded to the chromium complextreated pulp suspension, the additivematerials are attracted and caused to deposit uniformly upon the treatedpulp fibers. The pulp furnish so modified may then be processed in thenormal manner to produce various finished paper products.

The incorporation of a resin during the paper making process has severalattractive potentialities. Because the addition is accomplished duringthe making of the paper, the additional steps of coating or impregnatingof the finished paper and its attendant cost is avoided. Moreover,because the resin is incorporated while the fibers are separated, anextremely uniform dispersion of the resin about the fibers can result.

Although the exact nature of the reaction or mechanism responsible forthe present phenomenon is not fully known, it is believed that afunctional group of the chromium complex reacts with a functional groupof the cellulose molecule to form a bond in the nature of that of anaddition compound. So complete is the reaction, that when the additivematerial is dispersed in the reacted pulp suspension, it is completelyremoved from the aqueous phase, and the remaining Water becomesperfectly clear. The presence of the chromium complex then changes theelectrical charge surrounding the cellulose fiber. As a result, when aresin dispersion is subsequently added, the resin is attracted to thetreated fibers.

The compositions which are useful in the present invention may bepresented by the general structural formula:

CrClr This formula represents a Werner type chromium complex, wherein Ris an aliphatic hydrocarbon grouping. R may be either saturated orunsaturated, substituted or unsubstituted, and may contain additionalfunctional elements or groups, such as -SO -N, etc.

A commercial composition falling within the above empirical structureand which may be used in practicing the invention is marketed under thedesignation FC-'805 by Minnesota Mining and Manufacturing Company. Thepreparation of coupling agents of this class is generally disclosed inUS. Patent No. 2,662,835 issued to Reed, and comprises reacting chromylchloride with saturated perfiuoromonocarboxylic acids having from fourto twelve carbon atoms in the molecule, such as perfluoro-octanoic acid,in an inert anhydrous or solvent vehicle and in the presence of analcohol reducing agent or a hydrolyzed ammoniatedderivative thereof. Theparticular compound PC4305 is a chromium salt of a fatty acid in whichsome of the hydrogen has been replaced with fluorine, such asperfiuorocaprylic acid. Other complexes of this type such as disclosethe US. Patents No. 2,662,835, No. 2,642,416, No. 2,713,593 and No.2,934,450.

Another Werner type complex which may be used in the process accordingto the invention is marketed as Quilon by E. I. du Pontde Nemours 8:Company. This composition as disclosed in US. Patent 2,273,040 (February'17, 1942) is prepared by reacting chromyl chloride with a fatty acidsuch as stearic or palmitic acid in the presence of a reducing agentsuch as ethyl alcohol. The

formula of the complex may be represented as follows:

CuHss 'pulp is beaten to the desired freeness in order to open up andexpose the fibrillae to the necessary degree.

After the pulp has been sufliciently beaten, and the desired pulpfreeness has been attained, the beater roll is raised and the beateritself allowed to circulate, and stock is diluted and brought to aconsistency of between 1.5-

2.0%. The diluted chromium complex in the desired amount is then addedto the circulating pulp. To insure good circulation, the point ofaddition should preferably be before the raised beater roll. Thechromium complex reacts immediately with the beaten cellulose. Thecomplex appears to be absorbed on the surfaces of the fibrillae in theform of a molecular layer.

The time required for reacting the beaten pulp with the chromium complexvaries with the fiber consistency and the degree of circulation of thesuspension or slurry maintained during the treatment.

When water-soluble addition materials are used, some means should beprovided for insolubilizing them after they have been deposited on thefibers, so that when the finised paper product is subjected to water, orwater-vapor, the addition materials will not be removed. Where themodifying resin used is thermosetting, such as a phenolic resin, it'maybe added directly after the reaction of the coupling agent with thepulp. When urea formaldehyde or melamine formaldehyde resins are used,it has been found. to be very advantageous to include a waterdispersiprocess.

chest, machine chest, or other similar points in advance of niques.

lble resin accelerator or catalyst such as NH, salts, amine salts orinorganic non-ammoniacal salts, and to subject the finished paperproduct to a sufiiciently elevated temperature curing cycle to cause theresin to become crosslinked. When thermoplastic resins are employed, ithas been found to be advantageous to include additionally a minor amountof a thermosetting resin, such as urea or melamine formaldehyde, and aWater dispersible accelerator, and to subject the ultimate paperproducts to a temperature-curing cycle on the dry end of the papermachine to effect cross-linking and insolubilization of the resin.

The amount of chromium complex which need be used varies according tothe amount of modifying materials to be added and the type of product tobe fabricated. For example, it has been found that about 0.05 ofchromium complex solids, based on bone-dry fiber solids, willsufficiently condition pulp to'allow small quantities of resin to bethoroughly and completely incorporated. It has additional-ly been foundthat an amount of about 0.25% of chromium complex solids, based onbone-dry fiber solids, is sufiicient to-incorporate parts of a resinwith 100 parts of cellulose fibers. When larger quantities of chromiumcomplex is utilized, the pulp exhibits a greater freeness, but the greencolor of the chromium complex becomes apparent in the final product. At5% chromium complex solids addition, based on bone-dry fiber solids, ithas been found that the freeness of the treated furnish has increasedand the water drains rapidly upon the deposition of this treated furnishin the coaching box. Although amounts greater than 5% may be used,benefits from such increased addition fall off somewhat, and the endproducts take on a green color to an appreciable degree.

Additions of such materials as pigments or inert fillers should be madeto the beaten and reacted pulp at suitable points along the wet-endportion of the paper making Such suitable addition points are at thebeater themachine headbox. This results in thorough and uniformincorporation. The additive materials, such as inerts are formed into awater slurry. Prior to their incorporation with resin they maythemselves be treated with the chromium complex. Preferably, resins orrelated materials such as plasticizers and barrier inducing materialsshould be incorporated together with the pigment or filling material.Regardless of the treatment to which the filler materials are subjected,they should preferably be added 'to the reacted pulp as a homogenousmixture, since this accomplishes the wetting of the solid particlesprior to the addition, and aids in the subsequent reaction by which theparticles become attached to the cellulose fibers.

' Among the filler materials which may be used are barium sulfate,calcium carbonate, clay, diatomaceous silica, talc, titanium pigments,and zinc sulfide. Various dye stuffs and opacifying pigments, bothnatural and synthetic, serving as colorants, may be also added by thesame tech- They may be first treated with the chromium complex andcombined with any other solids constituting the chemical addition. Uponreaction of the fillers and the otheradditives with the treated pulp,the water becomes clear.

The resinous materials which are suitable for use in the presentinvention are those which can be readily dispersed in water by one ofseveral means. Even when they are not soluble many resins may beconditioned by techniques Well known to the art, such as by the additionof wetting agents, dispersing agents, or emulsifying agents. Most of theresins commonly used for modification and reinforcement in paper-makingmay be rendered compatible by means of one of the methods discussed.

The addition of the resin must be made after the pulp has beensufficiently beaten, and after it has been treated with the chromiumcomplex. The reason for this is that fibrillation of the pulp fibers ispromoted by the beating processes. The subsequent treatment of thefibers With the chromium complex makes available a large charged surfacearea for attaching the desired quantity of the resin. Where pigments orinert fillers are to be used in the system, they should preferably beadded as a water slurry and thoroughly mixed with the resin and therebycombined with the chromium complex treated pulp. Alternatively they maybe added as a water slurry immediately after the addition of resin. Theresin, in the form of an aqueous solution, suspension or an emulsion, isadded at a low solids content, such as about 2% to 5% total solids. Highsolids resin-containing varnishes, such as are used in the production ofelectrical board or postforming board stock, may not tolerate dilutionto this extent. Where this situation exists, the resin viscosity may bereduced with water to a point just short of the production of a cloudycondition. The diluted resin is subsequently added in small increments,rather than in the form of a steady stream.

A large variety of resinous materials may be employed, the choice beingdictated by the characteristic properties desired in the paper endproduct. For example, thermoplastic elastomeric latex resins may be usedfor flexibility, while less flexible resins may be used for barrierproperties and grease-proofness. Thermosetting resins such as phenolicsmay be used for rigidity and for electrical properties.

Among the synthetic fibers which may be used as modifying materials are:polyacrylic fibers (Orlon), polyester fibers (Dacron), or polyamidefibers (nylon). The fibers add strength to the final product and may beused to produce dimensionally stable papers, paper boards,pulp-moldings, and stereotype mats. Where polyester fibers such asDacron are used, they contribute both excellent dimensional stabilityand dielectric properties to the final product. Because of thehydrophobic nature of most synthetic fibers, it has been found desirableto soak them for a period of about sixty minutes prior to theirincorporation into the treated pulp. Soaking may be accomplished byplacing the fiber in an aqueous acidic solution, or in a solution of oneof the chromium complexes.

Other inorganic fibers, such as asbestos and ceramic fibers or metallicflakes and powders, may also be incorporated as modifiers for thepurpose of strengthening the paper product, or for obtaining otherproperties such as heat or electrical conduction or insulation. Asbestosor ceramic fibers may be pretreated by immersing them in a chromiumcomplex solution for a period of about 60 minutes prior to incorporationwith cellulose fibers. They are then added to the reacted pulp andblended prior to the addition of the resin.

The formulation to be used depends to a large extent upon the propertiesdesired in the end product. For example, long-fibered pulps areeffectively used in producing iost-forming board and electrical board,whereas shorterfibered pulps are used for fine papers. Synthetic fibersor inorganic fibers may be used to modify long-fibered stock in order toproduce dimensionally stable papers and stereotype mats. For theproduction of packaging and barrier papers, it has been found desirableto incorporate thermoplastic resins into the pulp. These may be usedalone or may be modified with thermosetting resins, or plasticizers toeffect such properties as heat sealing, waterproofness, greaseproofness,low moisture-vapor-transmission, and others. Thermosetting resins aregenerally used to produce post-forming boards which may be subsequentlycured to the infusible insoluble stage, and for the production ofelectrical boards. Particular chemicals may also be employed asadditives where particular properties are desired in the end product.

Among the paper making pulps which may be used in practicing theinvention are the following: alpha cellulose, cotton linters, rag,recovered broke, semi-chemical, sulfate, sulfite, soda, or mechanical.Any other papermaking pulp may also be employed.

The resins used as additive materials may be modified the propertiesdesired in the finished product.

by the addition of plasticizers of the conventional type which arecompatible With the particular resin used, and which are capable ofmodifying the resins in the desired manner, as for example phthalates,adipates, sabacates, dibenzoates, stearates, and polymeric materials.Other materials such as water soluble glycerides and glycols may aiso beused.

Among the pigments and inerts which may be added for particularproperties are titanium dioxide, various sulfates, clays, zinc sulfide,carbonates, silicates, dyestuffs, talc, and opacifying pigments, bothnatural and synthetic.

For water barrier type products various Waxes may be incorporated, suchas paraffin, microcrystalline wax, polyethelene, and other natural orsynthetic waxes.

A large variety of resins may be used as modifying agents according tothe present invention. As previously stated, in order to incorporate theresins it is necessary that they be dispersible in Water, since thepaper making process is primarily a water process. Thermoplastics suchas various vinyl derivatives, ethylenic resins, rosin and relatedcompounds, natural resins, chlorinated diphenols, cellulose esters andethers, natural and synthetic rubbers, phenolic resins in the novalacstage, and many others may be advantageously utilized. Where finishedproducts are desired which may be cured to the insoluble, infusiblestate, thermosetting resins such as phenolics, ureas, melamines, alkyds,polyesters, epoxies, silicones, and many others may be used. Watersoluble materials such as proteins, starches, carboxymethyl cellulose,glues, resins, caseins, etc., may also be employed.

For particular functional properties, specialized chemicals may beincorporated among which are mold-resistant chemicals,bacteria-resistant chemicals, insect-resistant chemicals,rodent-resistant chemicals, or flame-resistant chemicals.

The amount of chromium complex that may be incorporated is not critical,and will generally depend upon By using less than 5% of the complex tocondition the pulp, it is possible to incorporate a resin such as aphenolic in an amount equal to the weight of the dry pulp.

Amounts of the complex in the range of 0.05% to 5.0%, based on dryweight of pulp, have been found effective. Amounts greater than 5% maybe used where the increased color intensity is not detrimental.

A large number of various types of products may be formed by theprocesses included Within the scope of the invention. These products maybe classified in three main groups: products comprised of cellulosefibers modified by resin, products comprised of cellulose fibersmodified by the addition of a resin together with other fibers, andproducts comprised of cellulose fibers modified by the addition of aresin together with various filler materials other than fibers.

Among the important products of the first group are: post-formingfibrous board stock, electrical board, wet strength papers, barrierpapers, battery separators, and laminated structures.

Post-forming boards may be produced according to the present inventionby treating the beaten pulp with the chromium complex, and subsequentlyadding a suit able resin and treating by time-reacting in the aqueousstage. Among the resins which may be used are Waterdispersiblephenolformaldehyde resins, polyester resins, or epoxy resins.Thermosetting or heat-reactive resins are preferred as they may bemolded and cured subsequently to the formation of the board by heatingto temperatures in excess of 300 F., under molding pressure.

A preferred resin for the production of electrical board is aphenol-formaldehyde resole, or A stage resin, that is, one which is notyet advanced to the intermediate condensation state. The formed materialis subjected to temperatures of below 250 F. to drive off the water andis then ready for further processing.

' ness of 350 ml.

resin to the infusible and insoluble state.

High wet strength papers may be prepared in a manner similar to thatdescribed above by treatment with the chromium complex and subsequentlythe desired resin. The formed paper must then be heated to remove themoisture and cross-link and insolubilize the chromium complex and resincombination. Various resins such as acrylics, elastomers, vinyl polymersand copolymers, urea or melamine thermosetting resins, or combinationsof resins may be used.

Various fillers other than fibers may be used. Aluminum powder is suchan example. When the pulp is first beaten and then treated with thechromium complex, the treated aluminum flakes will be taken out ofsolution and deposited on the reacted pulp fibers when they aresubsequently incorporated with the resin into the pulp suspension.

Other additive fillers such as cork, sawdust, lignin, and other relatedproducts may be deposited on the pulp fibers by first treating with thechromium complex, as

described above. a

In order to test the prepared paper boards for resistance to peanut oil,an oil-wicking test is used in the following manner. Specimens of theboard are first freshly cut to size 4" long x 1" wide. Freshly cut sharpedges are needed as observation points to observe oil movement. On eachspecimen a line is drawn 1" from the bottom,

and four additional lines apart are drawn above the 1" line. The stripis immersed in peanut oil in a glass beaker, the oil being filled untilit reaches the one inch or bottom line. The time is recorded andmovement of the oil is noted over a period of time. Upward wicking ofthe oil is indicated by a darkening of the board.

Board which is completely impermeable to oil will, of course, exhibit nowicking over a long period such as '48 hours. However, for certainpurposes board in which wicking advances di in two and one half hours isacceptable.

Example A charge of 1000 grams of bleached pulps, on an airdry basis,constituting pine sulfate and 50% sulfite was introduced into a cyclebeater containing 12 gallons water. The pulp mixture was beaten to aCanadian free- One-half of the beater charge was retained and sufficientwater added to develop a consistency of 1.55%. Thereafter, ailuorochemical chromium com plex, identified as FC805, in an amountequal to 0.25% by weight of FC805 solids in relation to pulp solids, wasadded as a dilute aqueous dispersion to the moving pulp suspension inthe beater. The beater was used as a mixer with the beater roll raised.The FC-805 was added at the propeller shaft as a point of goodagitation. A timingreaction cycle of 15 minutes, under circulation,proved sufficient to complete the reaction. Completion of the reactionwas determined by taking a sample of the reacted pulp and adding it towater in a beaker. In a short time the reacted pulp solids separated andthe water was observed to be crystal clear. The pH of the solution was7.0.

Resinous additions were separately prepared constituting a total of 3%resin solids based on pulp solids. The resin addition comprised equalparts of polyethylene, polyvinylidene chloride, and melamineformaldehyde (80% solids). The first two resins were combined in theform of emulsions and diluted with water to a nonvolatile solids contentof about 5%. The melamine formaldehyde was weighed separately anddiluted with water. An insolubilizing salts, diammonium phosphate, in anamount equal to 30% by weight of the melamine formaldehyde, was Weighedand dispesred in water, and thereafter added and thoroughly incorporatedwith the melamine resin. The accelerated melamine formaldehydedispersion was then incorporated with the blended emulsions. The entireresin addition was then incorporated with the previously reacted pulpstock maintained under circulation. Reaction between the resins and thetreated pulp was immediate. An additional 15 minutes stirring period wasutilized to complete the reaction. The pH of the water remained at 7.0and a sample exhibited a tight complex structure with a crystal clearwater layer.

The consistency of the resinmodified pulp stock was determined and thevolume measured which would give 50 grams by weight of dry solids. Thestock was further reduced with water and placed in a couching box forboard-making. Drainage was rapid and formation was very good. The wetsheet was transferred to a press, and, after two pressings, the sheetwas supported between blotter stock and transferred to a sheet dryer.After one minute of drying on each side the sheet was placed on chipboard and given a smoothing operation by passing it through the nip ofthe steel rolls of a calender. The sheet was again placed on a dryer andeach si e again contasted for minute. A pass through tightened smoothingrolls resulted in a sheet having a very smooth surface. The sheet wasplaced on a dryer and dried to a constant weight. After the sheet hadbeen weighed, a caliper measurement was taken, and the sheet wasair-dried overnight at room temperature. It was subsequently conditionedfor 72 hours under standard air and humidity conditions.

An oil impermeability test as described above was performed by cuttingstrips from the sheet and immersing the strips in a vertical position ina container of peanut oil to determine edge-wicking resistance. Thestrips exhibited complete resistance to edge-wicking action over a 48hour period. A board exhibiting such high resistance to oil wicking issuitable for use as top liner in carton construction of packaging cakemix.

Example 2 One hundred grams, air-dry basis, of pulp furnish as preparedin Example 1 were added to a bell jar containing 5000 cc. water. Thediluted pulp stock was well circulated by a power driven agitator.FC-805, in an amount constituting 0.25% chromium complex solids based onpulp solids, was dispersed in water and added to the pulp stock.Circulation was continued for seven minutes to permit adequate mixing. Aresin mixture was then prepared consisting of equal parts by weight ofpolyethylene, polyvinylidene chloride, and melamine formaldehyde. Thefirst two resins were combined in the form of emulsions and diluted to asolids content of about 5%. The melamine formaldehyde was weighedseparately and diluted with water. An insolubilizing salt, diammoniumphosphate, in an amount equal to 30% by weight of the melamineformaldehyde was dispersed in water and incorporated with the melamine.A clay filler in an amount of 50% based on pulp solids was separatelywater-slurried and then combined with 6% non volatile solids of theresinous addition mixture, prior to incorporation with the treated pulp.The entire addition component was then incorporated into the dilutedpulp stock at moderate speed circulation. Reaction began immediately andcirculation was continued for five minutes. The pH of the solution atthis point was 7.0. A sulfuric acid/ alum solution was added in anamount sutlicient to bring the pH to 5.0. The aqueous phase at firstshowed cloudiness, but upon standing for four hours cleared completely.A board having a 0.15 inch caliper, prepared as in Example I, appearedto be well filled and exhibited an exceptionally smooth printingsurface, qualifying it as suitable as top liner material for cartoncontainers.

Example 3 Paperboard suitable for use as carton stock for dairy productswas prepared utilizing the basic process described in Example 1. Thepulp was first beaten to the desired freeness. To the beaten pulp wasthen added 0.25 by weight of FC-805 based on pulp solids. After thematerials were thoroughly reacted, 9% resins solids based on pulp solidswere added.

The resin solids had the following composition:

Polyethylene 33.33

Microcrystalline wax 33.33

Polyvinylidene chloride 16.67%

Melamine formaldehyde 16.67% (containing diammonium phosphate as anaccelerator).

Sufficient sulfuric acid/ alum solution was then added to adjust the pHof the solution to 4.5. Cyrstal clear white water was observed in thefinished stock upon standing for four hours. The pulp was then formed inthe couching box as in Example 1 and processed into finished board.

Example 4 A pulp furnish of 1000 grams of pulp (air dry basis) comprisedof 80% combined news print, patent coated liner scrap and kraftcuttings, and 20% beaten unbleached kraft was placed in a cycle beater.One hundred grams of the pulp combination (air-dry basis) were thenplaced in a bell jar containing 500 cc. water. Five percent Quilonsolids were added to the mixture in the bell jar. This relatively largeamount of chromium complex coupling agent was used because of the highpercentage of short fiber stock" contained in the news furnish. Mixingwas carried on for a period of 30 minutes to react the Quilon with thepulp.

A resinous addition utilizing the same resin mixture described inExample 1, in an amount of 6% solids based on pulp solids was added. Thereaction began immediatedly. An addition of alum solution was made untila pH of 5.0 was attained. When the reaction was complete, the waterbecame crystal clear.

A board was prepared as in the previous examples and, after drying andaging, was subjected to a peanut oil wicking test as described above.Vertical wicking was limited to inch in 2 /2 hours, indicating that theboard was suitable for use as a mid-filler material for carton containerstock.

Example This example illustrates the use of larger amounts of thecoupling agent than the previous examples. A beaten pulp stock wasprepared as in Example 1 and subsequently treated with 1% by weight ofQuilon, based on dry pulp solids. One half of the Quilon addition wasdirectly made to the pulp, and the other half was incorporated with thesubsequent resin addition, to act as an insolubilizer for the resin. Theresin addition totalled 12% resin solids based on dry pulp and had thefollowing composition:

Percent Polyvinyl acetate 50 Polyvinylidene chloride 33.3 Melamineformaldehyde 16.7

When the resin components were added to the reacted pulp, furtherreaction began immediately, and was furthere promoted by the addition ofacid to attain a pH of 4.5 in the slurry. The water phase became crystalclear.

Paper barrier board was formed from the pulp as in Example 1 andexhibited a green-grey cast as the result of the high Quilon content.This product is suitable for use where the color is not objectionable.

Example 6 Utilizing the process of Example 1, beaten pulp was treatedwith 0.25% FC-805 based on dry pulp weight.

A resin mixture comprised of one third melamine formaldehyde containingdiammonium phosphate as an accelerator in an amount equal to 30% byweight of the melamine formaldehyde, and two thirds polyvinyl acetatewas prepared. An amount of the resin combination calculated as 10% byweight solids based on the weight of dry pulp was separately prepared.Ten percent cork dust and 0.50% Quilon solids by weight based on corksolids were then separately combined in a water slurry, allowed toreact, and combined with the resin. This mixture was then added to themoving pulp stock and after complexing was followed by the addition ofsuiiicient acid and alum mixture to bring the pH of the solution to 5.0.

The treated pulp exhibited great freeness in couching, fast drainage andgood formation. Paper board was formed as in the examples above havinggood properties.

Example 7 Using the method of the examples above, bleached pulps weretreated with 0.25% Quilon based on dry pulp solids. An amount equal to6.25% of an emulsified nitrocellulose lacquer based on dry pulp Weight,containing 32% nitrocellulose, 28% resin, 20% plasticizer, and 20%polyvinyl alcohol was then complexed with the reacted pulp. Sullicientalum was added to adjust the water to a pH of 5.0. The watersubsequently became crystal clear. The treated pulp was formed into abarrier paper board as in the examples above.

Example 8 Beaten pulp stock prepared as in Example 7 was treated with0.375% Quilon by weight based on dry pulp. A 7.5% mixture of resinscontaining 83.30% nitrocellulose lacquer emulsion and 16.70%acrylonitrite rubber emulsion was added and completely incorporated intothe pulp stock. A barrier paperboard was produced from the treated pulpby the method described above.

Example 9 A barrier board was produced from bleached pulps prepared asabove by incorporating 6% Quilon solids based on dry pulp weight.Subsequently 12% resin solids based on dry pulp were added, followed bysufficient alum to lower the pH to 5.0. A board was prepared from thetreated pulp which had a green-grey color.

Example 10 A paperboard was prepared in a manner similar to the examplesabove for the following composition:

Pulp solids parts FC-805 0.25 (based on pulp solids) Hydroxyethylcellulose dispersion 0.06% solids (based on pulp solids) Resin mixture11% (based on pulp solids), containing:

Polyvinyl acetate 36.5% Melamine formaldehyde 9% Polyethylene 16.35%Micro-crystalline wax 38.15% Glyoxal 1.1% (insolnbilizer) The pulp wastreated at an adjusted pH of 7.5. The treated pulp was then formed intoboard as above.

Example 11 In order to demonstrate the method of incorporating a fillerhaving a large surface area, a paper board containing metal powder wasmade as follows.

Paper pulp was beaten and then treated with FC805 as in Example 2. Tenpercent by weight aluminum powder, based on pulp solids, was firstslurried with a Water dispersion of 0.2% Volan, also based on metalpowder solids. The slurry was then combined with a resin dispersionsimilar to that of Example 2 containing 9% resin solids by Weight basedon pulp solids. The entire mixture was added to the pulp suspension andthoroughly mixed. After standing for 4 hours the aqueous phase becameclear and colorless. Drainage was rapid l. .5. during the paper makingprocess, and there was no indication of free aluminum powder. Aftercalendering, the

paper sheet was smooth and bright.

Example 12 t A charge of 500 grams of mixed pulps, air dry basis, takenfrom a production beater, and which pulps had been beaten until aWilliams freeness of 315 had been attained, was placed in a cycleheater, and diluted with water to a consistency of 1.75 EC-805, in anamount of 0.25% based on pulp solids was added as a dilute aqueoussolution and reacted with the pulp solids under circulation for 20minutes. Subsequently, a separately prepared aqueous dispersion ofphenol formaldehyde resin in a quantity of 1.5% solids based on pulpsolids plus 23% inert fillers also based on pulp solids, werehomogeneously combined and incorporated into the reacted pulp stockwhich was then mixed for 15 minutes.

The consistency of the combined stock was then taken to determine theamount required to produce a mat having 75 grams dry weight. Thedetermined quantity of stock was couched off, pressed, and dried.

A stereotype mat was prepared and aged for one da coated with releasecoating, and tested by contact with molten lead at 600 F. plus. The matwas tested for dimensional stability and found to be satisfactory.

'Example 13 Into a batch of mixed pulps containing 500 grams pulp (dryweight) similar to that of Example 12, after dilution and conditioningwith FC-805, as in Example 12, then were further incorporated A inch 9micron glass fibers in an amount of 4% based on pulp solids. The glassfibers were previously water-wetted in a dispersion containing 0.25%Volan. Separately 23% inert fillers based on pulp solids were waterslurried. The glass fibers and slurried fillers were combined andincorporated with the moving stock. After the reaction was complete, thepulp was formed into a stereotype mat and tested as above as in Example12. It was found to be satisfactory for stereotype mat use. 7

Example 14 A beaten stock containing a combination of bleached pulps wastreated with 0.25% FC805 based on pulp solids. Amres 1420, a liquidphenol formaldehyde resin produced by American-Marietta Company wasadded in an amount equal to 10% resin solids based on pulp solids andcirculation continued until all solids were complexed. After 10 minutesstirring the pH solution was brought from pH 10 to pH by the addition ofacid/alum solution. The water at this point was crystal clear. Drainagewas very good and no sticking was experienced on the press. The resinwas well distributed throughout. Hand sheets having a weight of 45 gramswere produced from the treated pulp. After a cure of minutes at 325 F.,the board was rigid and appeared to be well suitedfor use aspost-forming board stock.

Example 15 A pulp stock was beaten and treated with FC-805 as in Example14. An epoxy-novolac resin was emulsified and a sufficient amount of theresin emulsion was then introduced to incorporate 15% resin solids basedon dry pulp. The pH of 9.0 was then reduced with acid/alum solution of apH 5.0. Observation of a sample of the stock indicated that allingredients had migrated to the pulp and a crystal clear waterseparation resulted.

Sheets were prepared as in Example 14 above and exhibited extremely goodresin distribution and increased edge tearing resistance.

Invention is claimed as follows:

1. A process for depositing a water-dispersible resin on cellulose pulpfibers comprising first dispersing a coupling agent into an aqueoussuspension of said fibers, and subsequently dispersing said resin intosaid suspension, said coupling agent consisting essentially of a water-12 soluble chromium coordination complex of an acyclic acido carboxylicacid.

2. A process according to claim 1 wherein said coupling agent consistsessentially of stearato chromic chloride.

3. A process according to claim 1 wherein said coupling agent consistsessentially of methacrylato chrornic chloride. 2

4. A process according to claim 1 wherein said coupling agent consistsessentially of a Werner-type chromium coordination complex of aperfluorocarboxylic acid.

5. A process according to claim 1 wherein said coupling agent consistsessentially of a chromium coordination complex of a saturatedperfluorocarboxylic acid having from 4l2 carbon atoms.

6. A process for depositing a resin on beaten cellulose pulp fiberscomprising first adding a coupling agent to an aqueous suspension ofsaid fibers and mixing said suspension to deposit said coupling agent onsaid fibers, and subsequently adding an aqueous dispersion of said resinto said suspension and mixing said suspension until said resin isdeposited on said fibers, said coupling agent consisting essentially ofa water-soluble chromium coordination complex of an acyclic acidocarboxylic acid.

7. A process according to claim 6 wherein said coupling agent consistsessentially of stea-rato chromic chloride.

8. A process according to claim 6 wherein said coupling agent consistsessentially of methacrylato chromic chloride. 7

9. A process according to claim 6 wherein said coupling agent consistsessentially of a Werner-type chromium coordination complex of aperlluorocarboxylic acid.

10. A process according to claim 6 wherein said coupling agent consistsessentially of a water-soluble chromium coordination complex of asaturated perfluorocarboxylic acid having from 4-12 carbon atoms.

11. A process for depositing an adherent coating of a water-solubleresin with cellulose pulp fibers comprising the steps sequence ofbeating an aqueous suspension of said fibers until they have attained asuitable dreeness, adding an aqueous solution of a coupling agent tosaid suspensicnand continuously circulating said suspension until saidcoupling agent has been substantially deposited on said fibers, andadding an aqueous dispersion of said resin to said suspension and mixingsaid suspension until said resin has been substantially deposited onsaid fibers, said coupling agent consisting essentially of awater-soluble chromium coordination complex of an acyclic aoidocarboxylic acid.

'12. A process according to claim 11 wherein said coupling agentconsists essentially of stearato chromic chloride.

13. A process according to claim 11 wherein said coupling agent consistsessentially of methacrylato chromic chloride.

14. A process according to claim 11 wherein said coupling agent consistsessentially of a Werner-type chromium coordination complex of aperfiuorocarboxylic acid.

15. A process according to claim 11 wherein said coupling agent consistsessentially of a water-soluble chromium. coordination complex of asaturated perfiuorocarboxylic acid having from 4-12 carbon atoms.

16. A process for the production of resin-modified paper which comprisesthe steps sequence of dispersing a coupling agent into an aqueoussuspension of beaten cellulose pulp fibers, dispersing awater-dispersible resin and an inert filler into said suspension, andforming said pulp fibers into paper on a paper-making machine, saidcoupling agent consisting essentially of a water-soluble chromium:coordination complex of an acyclic acido carboxylic acid.

17. A modified paper product which may be molded to a permanent shape atelevated temperature and pressure, said paper product having beenprepared by the steps in sequence of dispersing a coupling agent into anaqueous suspension of beaten cellulose pulp fibers, dispersing awater-dispersible resin into said suspension, and forming said paperfrom said pulp fibers on a paper making machine, said coupling agentconsisting essentially of a water-soluble chromium coordination complexof an acyclic acido carboxylic acid.

References (IiteaZ in the file of this patent UNITED STATES PATENTS llerOct. 10, 1944 Pattilloch Nov. 10, 1953 McQuiston Ian. 19, 1954 Cilley eta1 Nov. 27, 1956 Collier July 30, 1957 Hawley et al Apr. 12, 1960Pattilloch Ian. 9, 1962 Martin May 29, 1962 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,109,769 November 5, 1963 Ray C.Martin It is hereby certified that error appears in the above numberedpatent requiring correction and that the said Letters Patent should readas corrected below.

Column 2, line 13, for "absorbed read adsorbed column 7, line 75, for"salts" read salt column 8, line 2, for "dispesred" read dispersed line25, before "minute" insert one column 9, line 26, for "500" read 5000lines 62 and 63, for "furthere" read further column 10, line 67, before"aluminum" insert of Signed and sealed this 21st day of April 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J, BRENNER Attesting Officer Commissioner ofPatents

1. A PROCESS FOR DEPOSITING A WATER-DISPERSIBLE RESIN ON CELLULOSE PULPFIBERS COMPRISING FIRST DISPERSING A COUPLING AGENT INTO AN AQUEOUSSUSPENSION OF SAID FIBERS, AND SUBSEQUENTLY DISPERSING SAID RESIN INTOSAID SUSPENSION, SAID COUPLING AGENT CONSISTING ESSENTIALLY OF AWATERSOLUBLE CHROMIUM COORDINATION COMPLEX OF AN ACYCLIC ACIDOCARBOXYLIC ACID.